🌤 Weather at Keens Mill by season
| Spring | Summer | Fall | Winter |
|---|---|---|---|
| 29–74 °F | 58–88 °F | 32–80 °F | 19–46 °F |
Each range runs from the coldest monthly average low to the warmest monthly average high in that season (1991-2020 climate normals), measured at Lambertville, 3 mi away, elevation 68 ft. Conditions at the park can differ from the station, especially where elevation differs — check a forecast before you go.
New Jersey’s Historic Gristmill — Built by George Keen in 1838, Site of Revolutionary War-Era Mills, Swartswood Lake Area, Stillwater Township Sussex County New Jersey
Keens Mill is a historic mill site in the Swartswood Lake area of Stillwater Township, Sussex County, New Jersey. The mill was constructed by George Keen in 1838 on the site of an earlier mill established by Charles Rhodes. The location has hosted milling operations dating back to the Revolutionary War era, making it one of the longest-running mill sites in Sussex County. The site features a historic stone gristmill structure, connections to the broader Swartswood Lake recreational area, proximity to Swartswood State Park, and interpretation of New Jersey’s agricultural and industrial heritage.
Milling Heritage
Water-powered gristmills were the economic engines of rural New Jersey in the 18th and 19th centuries. The Keens Mill site exemplifies this heritage — with mills operating here since the Revolutionary War era, generations of Sussex County farmers relied on this location to grind their grain into flour. George Keen’s 1838 mill building represents the mature period of water-powered milling technology in northern New Jersey.
Swartswood Lake Area
Keens Mill sits near Swartswood Lake, one of the largest natural lakes in New Jersey and home to Swartswood State Park. The area offers excellent fishing, boating, swimming, and hiking, making it a natural complement to a visit to the historic mill site. The broader Stillwater Township area preserves much of its rural agricultural character, offering a glimpse into the landscape that sustained communities like the one that depended on Keens Mill.
Frequently Asked Questions
Is Keens Mill open to the public?
The mill is a historic site. For current access information, contact the Historical Society of Stillwater Township.
What is nearby?
Swartswood State Park is nearby, offering swimming, boating, fishing, camping, and hiking.
Wildlife & Nature
Keens Mill — a historic mill site in the New Jersey park system. The mill’s stream, pond, and surrounding forest support great blue herons, wood ducks, and painted turtles. Brook trout may inhabit the cold stream.
Nearby Attractions
Local New Jersey communities — surrounding.
Keep exploring: The closest neighbors are The Marshall House (a short drive away) and Delaware and Raritan Canal State Park Trail (a short drive away).
🐾 Dogs & Pets at Keens Mill
- Pets allowed? statewide rule
- Pets are allowed in NJ state parks and forests on leash but are prohibited from buildings, swimming beaches and non-designated campsites.
- Leash rule statewide rule
- Leash 6 feet or less, with the pet under physical control at all times.
- Beaches & swim areas statewide rule
- Pets are prohibited from swimming beaches and swimming waters statewide.
- Cabins & lodging statewide rule
- Pets are prohibited from cabins/lodging; the Pet Friendly Camping Program designates campsites at 13 areas (e.g. Round Valley all sites, Allaire 1-8, Bass River 1-85, Stokes 101-137) for up to two dogs or cats per permit.
- Pet fees statewide rule
- $5.00 per night additional charge for a pet-friendly campsite; no day-use pet fee.
- Statewide exceptions statewide rule
- Pet Friendly Camping requires current rabies vaccination with written proof at check-in; caged birds/reptiles only allowed inside RVs.
Are dogs allowed at Keens Mill?
Pets are allowed in NJ state parks and forests on leash but are prohibited from buildings, swimming beaches and non-designated campsites. Individual parks can post stricter rules — check signage on arrival.
Rules verified July 2026 via dep.nj.gov. More: New Jersey state parks guide · Dog rules in all 50 states compared
Park Location
Plan your gear for Keens Mill
From our editorial guides, matched to this park’s activities:
